Coded track circuits



Dec. 26, 1944.

H. G. BLOSSER CODED TRACK CIRCUITS Filed Sept. 28, 1945 IN V ENTOR Herman G .B [an/'01.

H15 ATTORNEY wam Patented Dec. 26, 1944 UNITED STATES P ENT OFFICE CODED TRACK CIRCUITS Herman G. Blosser, Pittsburgh, Pa., assignor to The Union Switch & 'Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application September 28, 1943, Serial No. 504,133

. relay is interrupted are correspondingly increased 5. Claims.

My invention relates to a railway signaling system of the coded track circuit type in which impulses of feedback energy are supplied to the section rails at the entrance end thereof in the intervals between impulses of master code and operate a detector relay at the exit end of the section to indicate occupancy of the track section at that point.

In some situations it is desirable to divide a track section into two subsections and to employ the track relay of the forward subsection to control the supply of coded energy to the rails of the rearward subsection. In order to equalize the on and off periods in the coded energy supplied to the rails of the rearward subsection it may be desired to arrange the apparatus so that energy is supplied to the rails of therearward subsection over a circuit including a back contact of the track relay for the forward subsection.

Where a feed back detector relay of the polar stick type is employed the equipment is arranged so that this relay is connected across the section rails during the off periods in the coded energy supplied to the section rails so that energy sup-' plied over the section rails will move the relay of C. E. Staples and myself there is a short time.

interval from the instant the supply of master code to the section rails is cutoff until feed back energy is supplied over the section rails and operates the detector relay'contacts. If energy is supplied to the detector relay at the start of each on period in the code supplied to the section rails the contacts of thedetector relay will occupy the position to which they are moved by feed back energy a substantially smaller proportion of the time than they occupy the other one of their two positions. This reduction in the time that the detector relay contacts occupy the position to which they are moved by feed back energy necessitates the use of an approach relay vhaving a low resistance winding, while'the use of a relay with a low resistance winding increases the energy consumed by this relay and increases wear on the contact of the detector relay which controls the circuit of the approach relay. In addition, if the time that the detector relay contacts occupy the positionto which they are moved by feed back energy is reduced, the periodsdui ing which the supply of energy to the approach and the release time of this relay must be increased to insure that the relay will remain picked up during the periods in which the circuit of the relay is interrupted. Accordingly, the

ergy is supplied after the relay contacts pick up,

and which serves to hold the relay contacts picked up throughout the ofi periods in the code supplied to the section with which the relay is associated. If the supply of energy to this holding winding is interrupted at the start of each on period in the code, the'contacts of the detector relay will be picked up for substantially less than one half of the time and the time during which energy is supplied to the approach relay is correspondingly reduced and the operating difliculties described above are encountered with the approach relay.

It is an object of this invention to provide improved means for use at a cut section Where back contact coding is employed to control the supply of energy to the detector relay for the rearward subsection so that movement of the relay contacts is delayed substantially as long at the start of an on; period in the code supplied to the section rails as movement of the relay of an off period in the code.

Afurther object of the invention is to provide improved apparatus of the type described employing a feed back detector relay of the polar stick typeand incorporating means for delaying the supply of energy to the relay at the start of each on" period in the code to thereby delay responseof the relay at these times.

Another object ofv theinvention is to provide improved apparatus of the type described employing a =feed back detector relay of the polar biased neutral type and incorporating means for delaying interruption-of the holding circuit for the relay at the start of each on period in the code to thereby delay release of the relay at such times. H

Other objects of the invention and features of novelty will be apparent from the following description taken in connection with the accompanying drawing.

I hall describe two forms of coded track circuit apparatus embodying my invention and shall then point out the novel features thereof in claims.

In the drawing Fig. 1 is a diagram of a section of railway track equipped with track circuit apparatus employing feed back detector relays of the polar stick type and having the equipment at the cut section arranged as taught by this invention, and

Each location in the track stretch is provided with a suitable source of direct current, such as a storage battery, not shown, the terminals of which are designated B and C in the drawing, while the alternating current cab signal control I energy is supplied from a suitable source, not

Fig. 2 is a fragmentary view showing how the cut section apparatus may be arranged where a feed back detector relay of the polar biased neutral type is employed. Similar reference characters refer to similar parts in each of the two views.

In practicing my invention I employ a contact of the impulse relay which controls the supply 'of feed back energy to the rails of the, forwardsubsection to control the circuit of the detector relay for the rearward subsection, instead of employing a contact of the track relay for this purpose as heretofore. On release of the track relay there is a short time interval until the contacts of the impulse relay pick up and this time interval is substantially as long 'as the period from picking up of the track relay contacts until response of the detector relay to feed back energy supplied over the sectionrails so that this arrangement operates to substantially equalize the periods during which the detector relay contacts occupy each of their two positions.

Referring to Fig. 1 of the drawing there is shown therein a section of railway track through which traffic normally moves in the directionindicated by thearrow, that is from left to right. The track rails l and'2 are divided by insulated joints 3 into track sections, whil the rails of the track section shown in the drawing are divided by insulated joints 3 into a first or forward subsection A2T and a second or rearward subsection BZT. Each of these subsections is provided with track circuit apparatus of the type employing coded energy, while the track circuit apparatus for each subsection includes means for supplying coded alternating current to the section rails (when the'section'is occupied to operate'cab signal apparatus on a locomotive present in the section.

This invention is directed particularly to the apparatus at the junction-between the-sections AZT- and BZT, and the equipment at the exit end of section AZT and at the entrance end of section BET- may be arranged in any appropriate mannerwell-known in-the art; In thedrawing the equipment at the exit end of sectionAZT is arranged as shown in the above identified'application of C. E. Staples and myself, while the equipnected across the section railsat the exit end..ofv

the section. The supply of master code energy to the rails of the forward subsection is controlled by a coding relay CR, while the coding relay CR is operated at one or anotherof a plurality of different rates governed by traffic condi-- tions in advance,

. The equipment is shown in the condition which it assumes when the track section is vacant. When the contacts of coding relay CR are picked up its contact [0 interrupts the circuit of the trackiwinding ll of detector relay AZK and connects the track battery AZTB and the track transformer AZ'IT across the-section rails. At this timeenergy flows from the positive terminal of the battery AZTB to track rail I, through the winding of track relay AZTR from left to right, over back contact H of relay AZIR, track rail 2 and front contact ll] of relay CR to the negative terminal of the battery. In addition, when the contacts of relay CR are picked up contact l4 establishes the circuit of the local winding I5 of relay A2K and causes the contact I6 of this relay to move to its right hand or reverse, position in which it interrupts the circuit of approach relay A2AP. i

The energy supplied from the track battery A2TB picks up the contacts of track relay A2TR with the result that contact I8 of relay AZTR connects the track winding. 19 of detector relay BZK across the rails of sectionBZT and interrupts the circuit for supplying energy from the track battery BZTB to therails, of section BIT.

As the supply of energy from the track battery B2TB to the rails of section BZT is cut off the contacts of track relay B2TR are released, while on release of the'contacts of relay BZTR an impulse of energy is supplied from the decoding transformer BZDT to the impulse relay B2IR and picks up the contacts of relay B2IR momentarily to cause an impulse of energy to be supplied from' the battery BZFB to the detector relay BZK over the circuit which is .traced from the positive terminal of the battery B2F B over front contact 20 of relay BZIR, winding of relay BZTR from right to left, trackrail I, winding [9 of relay B2K, front contact l8 of track relay AZTR, and track rail 2 to the negativeterminal of the battery B2FB. The energy supplied from the battery B2FB to relay B2K moves the contact 22 of relay 132K to its left hand or normal position in which it establishes the circuit of approach relay BZAP, while the operating characteristics of the relay BZK are such that the relay contact remains in its normal position after the contact 20 of relay BZIR releases and cuts off the supply of energy from the batterypBZIR.

The energy supplied to relay BZAP over normal polar contact 22 of. relay B2K' picks up contact 23 of relay BZAP to preventthe supply of energy to the primary. winding of transformer B2TT and to short circuit this winding to minimize arcing at back contact l8 of the track relay A2TR.

On release of the contacts ofcoding relay CR, contact l4 interrupts the circuit of the local winding 15 of relay AZK, while contact 10 of relay CR interrupts the circuit of the track battery AZTB and connects the track winding ll of relay AZK across the rails of section AZT. On

winding 19 of relay 32K and connects the track battery B2'I'B across the rails of section B2T so that energy from battery B2TB feeds to track relay BZTR- and picks up its contacts. On picking up of the contacts of the track relay B2TR an impulse of energy is supplied from transformer BZDT to relay BZIR but the polarity of this impulse is such that it is ineffective to pick up the contacts of relay BZIR.

In addition on release of the contacts of relay AZTR. an impulse of energy is supplied from the decoding transformer A2DT to the impulse relay AZIR to pick up its contacts momentarily. On picking up of relay AZIR its contact l2 connects battery A2FB across the rails of section A2T and energy is supplied from this battery to rela A2K over the circuit which is traced from the positive terminal of the battery through the winding of track relay A2TB from right to left, track rail I, track winding H of relay A2K, back contact H! of relay CR,- and track rail 2 to the negative terminal of the battery. The energy supplied from the battery AZFB to the relay A2K moves the contact l6 of this relay to its left hand or normal position in which it establishes the circuit of relay AZAP, while the contact I6 remains in its normal position after relay A2IR releases and cuts off the supply of energy from the battery AZFB to relay A2K. The energy supplied over contact l6 of rela A2K to relay A2AP picks up the contacts 25 of this relay to thereby prevent the supply of energy to the primary winding of transformer A2TT and to short circuit this winding to reduce arcing at front contact III of relay CR. The relay A2AP isof a type the cpntact of which is slow to release so that the relay contact remains picked up during the periods in which the contact l-G of relay A2K is normally in its reverse position.

On picking up of the contacts of relay A2IR its contact 26 establishes the circuit of the local winding 28 of relay 32K and causes the contact 22 of relay 32K to mov to its right hand or reverse position in which it interrupts the circuit of the rela B2AP. The supply of energy to winding 28 of relay B2K is interrupted as soon as relay AZIR releases, but the contact 22 of relay 132K will move to its reverse position before i relay AZIR releases and will remain in its reverse position after relay A2IR releases.

During the next picked up period of the contacts of the coding relay CR energy is supplied to the local winding'of relay A2K, and is supplied from track battery A2TB over the rails of section A2T to the track relay A2TB and picks up its contacts to interrupt the supply of energy from track battery B2TB to the track relay BZTR and to connect the track winding IQ of relay B2K across the rails of section B2T. On release of the track relay BZTR the rela BZIR picks up to supply an impulse of feed back energy from battery B2FB to relay B2K to move its contact 22 to its normal position in which it establishes the circuit of relay B2AP.

As a result of code following operation of the track relaysBZTR and A2TB. energy is supplied through the decoding transformers BZDT and A2DT to the relays B2H and A2I-I to keep their contacts picked up. Similarly, as long as the section is vacant, the contacts of the detector relays 32K and A2K are moved to their reverse position during each on period in the code supplied to the associated section, and are moved to their normal-positions by feed back energy supplied over the section rails during each "off period in the code.

As pointed out above, on picking up of the contacts of track relay A2TR the circuit of the I track battery BZTB is interrupted and the track winding [9 of relay BZK is connected across the rails of section B2T. On interruption of the circuit of the track battery B2TB the track relay BZTR. releases so that energy is supplied through the decoding transformer B2DT to relay B2IR and its contacts "pick up to cause energy to be supplied from battery B2FB to relay 32K to move contact 22 to its left hand or normal position in which it establishes the circuit of relay B2AP.

It will be seen that some time elapses from the instant the contacts of track relay A2TB pick up to start the oil period in the code supplied to section B2T, and the instant at which feed back energy supplied over the section rails moves the contact of relay 32K to its normal position to establish the circuit of relay B2AP.

The apparatus vprovided by this invention is arranged so that on release of the track relay AZTR to initiate an on period in the code supplied to section B2T, energy is not supplied to the local winding 28 of relay BZK immediately. Instead, the supply of energy to this winding is delayed until the relay A2IR picks up, and this does not occur for an appreciable time interval subsequent to release of the contacts of the track relay A2TB. Accordingly, contact 22 of relay B2K remains in its left hand or normal position and maintains the circuit of the relay BZAP for a period subsequent to the start of an on period in the code supplied to section BZTR. The delay in the supply of energy to the local winding of relay .B2K after release of track relay A2TB to initiate an on period in the code supplied to section B2T is almost as long as the delay in the supply of feedback energy to the relay 132K after picking up of the track relay A2TB.

to initiate an ofi period in the code supplied to section B2T. This delay in the supply of, energy to relay 132K on release of the track relay AZ'I'R substantially increases the length of the periods during which contact 22 of relay BZK establishes the circuit of relay BZAP and correspondingly decreases the periods during which the circuit of relay BZAP is interrupted.

This increase in the proportion of the time that energy is supplied to the relay B2AP, and the decrease in the length of the periods during which the relay contacts must remain picked up while the supply of energy to the relay winding is interrupted, makes possible the use of a relay with a much higher resistance winding than would otherwise be required. The high resistance relay which this invention makes it possible to use consumes less energy than would be required by a lower resistance relay, while the decrease in the energy in the circuit of the relay results in less wear on the contact 22 of relay BZK control: ling this circuit.

The reduction in the release time of the relay BZAP made possible by the reduction in the length of the periods during which the relay contacts must remain picked up results in. more prompt release of the relay when a train enters the track section.

Where a train moving in the normal direction of traffic enters section B2T the track relay BZTR is shunted and ceases to follow code so relay B2I-I releases, while relay BZIR remains released and feed back energy is no longer supplied to the section rails. Accordingly, contact 22 of relay 32K is not moved to its normal position to estab lish the circuit of relay B2AP, but remains in its reverse position in which it interrupts the circuit of this relay, and after a short period contact 23 of relay B2AP releases and establishes the circuit of the [primary winding of track transformer B2TT so that on continued. operation of the track" relay AZTR coded alternating current is supplied to the rails of section B2T to operate the cab signal apparatus on the locomotive in that section.

When the train advances into section A2T the track relay AZTR ceases to follow code and relay A2I-I releases and its contact interrupts the circuit of the track battery B2TB and of the track transformer B2'IT to thereby cut off the supply of energy to section B2T. In addition, at this time relay A2IR remains released. so energy is no longer supplied from battery A2FB to relay A2K and its contact 16 remains in its reverse position in which it interrupts the circuit of relay A2AP. Accordingly, relay A2AP' releases and its contact 25 establishes the circuit of the primary winding of transformer AZTT so that on continued operation of coding relay CR coded alternating current is supplied to the rails of section A2T to operate the cab signal apparatus on the locomotive while it is in that section.

When section A2T is vacated coded energy again feeds to track relay A2TR and operates it so that relay A2I-I is picked up and establishes the circuit of the track battery BZTB so that energy from this battery is supplied to track relay BZ'I'R. As a result of operation of the track relays the impulse relays operate to supply feed back energy to the section rails to cause the detector relays to establish the circuits of the approach relays so that the contacts of the approach relays pick up and cut off the supply of energy to the track transformers.

In Fig. 2 there is shown cut section apparatus employing a feed back detector relay B2KA of the. biased polar neutral type. The relay B2KA is arranged so that its contacts pick up only when energy flows through the relay from left to right,. while the approach relay B2AP is energized in series with the local or holding winding 28 of relay B2KA over a circuit which includes front contact 22 of relay B2KA and back contact 26 of relay A2IR. The modification shown in Fig. 2 is otherwise the same as that shown in Fig. 1.

When the track relay A2TR is picked up its contact l8 interrupts the circuit of track battery BZTB and connects the track winding 19 of relay B2KA across the rails of section 132T. During this off period in the code supplied to section B2T the equipment at the entrance end of this section operates as explained in connection with Fig. 1 to supply an impulse of feed back energy over the section rails to relay B2KA and its'contact 22 picks up and establishes the circuit including back contact 26 of relay A2IR for energizing the holding winding 28 of relay B2KA and the winding of relay BZAP in series. The energy supplied to winding 28 of relay B2KA keeps the contact of this relay picked up while. the energy supplied to relay B2AP holds its contact 23 picked up so that energy is not supplied to the primary winding of transformer B2TT.

On release of the contacts of track relay A2TR contact l8 interrupts the circuit of the track winding IQ of relay B2KA and connects the track battery BZTB across the rails of section BZT. In addition, on release of the contacts. of track relay AZTR an impulse of energy is sup.-

aces-299 plied through the transformer A2DlI .to relay A2IR to pick up its contacts momentarily and cause an impulse of feed back energy to be supplied to the rails of section A2T. Also on Picking up of relay A2IR' its contact 26 interrupts the circuit for energizing the relay BZAP and the holding winding 28 of relay B2KA in series and contact 22 of relay B2KA releases to additionally interrupt this circuit and prevent it from being reestablished on release of relay AZIR. At this time, therefore, the supply of energy to the winding of relay BZAP is cut off, but because of the. slow releasing characteristics of the relay, its contact 23 remains picked up and interrupts the circuit of transformer B2TT.

On the next movement of the contacts of track relay AZTR to their picked up position contact l8 cuts off the supply of energy from battery BZTB to the rails of section B2T and connects the track winding I9 of relay B2KA across the rails of section B2T so that ,feed back energy supplied to the section rails at the entrance end of the section feeds to the relay B2KA and itscontact 22 picks up to establish the circuit for energizing the relay BZAP and the holding winding 28 of relay B2KA in series. The energy supplied over this circuit keepsthe contact 22, of relay B2KA picked up to maintain the circuit, while this en- On subsequent release of the contacts of the track relay AZTR the circuit of relay BZAP is not interrupted until relay A2IR picks up, and, as pointed out in connection with the modification shown in Fig. 1, relay A2IR does not pick up for an appreciable time interval after the contacts of the track relay A2TR release. Ac-

cordingly, the circuit of relay BZAP is maintained somewhat longer than it would be maintained if the circuit of this relay were controlled by the track relay instead of by the impulse relay.

The increase which the circuit produces in the length of the periods during which energy is supplied to the relay BZAP, and the corresponding decrease in the length of the periods during which the contacts of the relay must remain picked up while the supply of energy to the relay is interrupted, makes possible the use of a relay with a higher resistance winding than would otherwise be required. As explained in connection with Fig. 1 this results in a reduction in the current consumed by this relay and a reduction in the wear on contact 22 of relay B2K controlling the circuit of relay BZAP.

When a train enters section B2T the supply of feed back energy over the section, rails is cut off and the contact of relay B2KA remains released and does not establish the circuit of the relay BZAP and after a short period its contact 23 releases and establishes the circuit of the track transformer so that coded alternating current issupplied to the rails of section B2T;

Although I have herein shown and described only two forms of coded track circuit apparatus embodying my invention, it is understoodv that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a stretch of railway track including adjacent first and second track sections, said first track section being equipped with coded track circuit apparatus includinga code following track relay having associated therewith an impulse relay having normally released contacts movable to a picked up position in which they establish a circuit to supply energy. to the rails of said first section, means responsive to release of the track relay contacts for supplying to said impulse relay energy effective to pick up the relay contacts momentarily, means including a back contact of said track relay for supplying energy to the rails of said second section, means including a front contact of said track relay for connecting a winding of a code following detector relay across the rails of said second section, said second section being equipped with track circuit apparatus effective when the section is vacant to supply to said detector relay over the section rails in theperiods in which the detector relay is connected across the section rails'energy tomove the detector relay contacts from their first to their second position, an approach relay, a circuit governed by a contact of said detector relay for supplying energy to said approach relay,

including adjacent first and second track sections,

said first track section being equipped with coded track circuit apparatus including a code following track relay having associated therewith an impulse relay-having normally released contacts movable to a picked up position in which they establish a circuit to supply energy to the rails of said first section, means responsive to release of the track relay contacts for supplying to said impulse relay energyeifective to pick up the relay contacts momentarily, means including a back contact of said track relay for supplying energy to the rails of said second section, means including a front contact of said track relay for connecting a winding of a code following detector relay across the rails of said second section, said second section being equipped with track circuit apparatus efiective when the section is vacant to supply to said detector relay over the section rails in the periods in which the detector relay is connected across the section rails energyto move the detector relay contacts from their first to their second position, an approach relay, a

a code following detector relay across the rails of said second section, said second section being equipped with track circuit apparatus effective when the section is'vacant to supply to said detector relay over the section rails in theperiods in which the detector relay is connected across the section rails energy to move the detector relay contacts from their first to their second position, an approach relay, a circuit for supplying energy to said approach relay when the contacts of said detector relay are in their second position, and means including a circuit gov erned by a contact of said impulse relay and controlling movement of the contact of said detector relay from its second to its first position.

4. In combination, a stretch of railway track including adjacent first and second track sections, said first track section being equipped with coded track circuit apparatus including a code following track relay having associated therewith an impulse relay having normally released contacts movable to a picked up position in which they establish a circuit to supply energy to the rails of said first section, means responsive to release l of the track relay contacts for supplying to said impulse relay energy effective to pick up the relay contacts momentarily, means including a back contact of said track relay for supplying energy to the rails of said second section, means including a front contact of said track relay for connecting a winding of a polarized code following detector relay across the rails of said second section, said second section 'being equipped with track circuit apparatus effective when the section is vacant to supply to said detector relay over the section rails in the periods in which the detector relay is connected across the section circuit governed by a contact of said detector relay for supplying energy to said approach relay, and means including a circuit governed by a contact of said impulse relay and controlling movement of the contact of said detector relay from its second to its first position.

3. In combination, astretch of railway track including adjacent first and second track sections, said first section being equipped with coded track circuit apparatus including a code following track relay having associated therewith an impulse relay having normally released contacts movable to a picked up position in which they establish a circuit to supply energy to the rails of said first rails energy to move the detector relay contacts to their normal position, an approach relay, a circuit including a normal polar contact of said detector relay for supplying energy to said approach relay, and a circuit including a front contact of said impulse relay for supplying energy to said detector relay to move its contacts to their reverse position.

5. In combination a stretch of railway track including adjacent first and second track sections, said first track section being equipped with coded track circuit apparatus including a code following track relay having associated therewith an impulse relay having normally released contacts movable to a picked up position in which they establish a circuit to supply energy to the rails of said first section, means responsive to release of the track relay contacts for supplying to said impulse relaytenergy effective to pick up the relay contacts momentarily, means including a back contact of said track relay for supplying section, means responsive to release of the track relay contacts for supplying to said impulse relay energy effective to pick up the relay contacts momentarily, means including a back contact of said track relay for supplying energy to the rails of said section, means including a front contact of said track relay for connecting a winding of energy to the rails of said second section, means including a front contact of said track relay for connecting .a winding of a code following detector relay across the rails of said second section, said second section being equipped with,

ing its own front contact and a back contact of said impulse relay, an approach relay, and means for energizing said approach relay when the contacts of said detector relay are picked up.

HERMAN G. BLOSSER. 

